Recently, increasing use has been made of concealed plumbing fixtures, where the building owner can postpone his decision on the precise type of concealed plumbing fixture he desires until the final phase of interior works on a building. First of all, simply a universally usable connecting member is installed in an installation opening of the building wall, for example a wall recess, and is connected to the water pipes laid in the building wall, thus in particular the domestic cold water pipe, the domestic hot water pipe and optionally mixed-water-discharging pipes. The wall recess thus equipped is then covered until the interior works on the building have been largely completed. Only then is the covering of the wall recess removed again. The building owner now decides which specific type of concealed fitting he desires, for example a single-lever mixer, thermostatic valve or the like. The manufacturer of the concealed fixture has available a complete set of functional units which are standardised such that they can all be connected to the same connecting member, but contain different sanitary valves. The specific functional unit desired by the building owner is then connected to the connecting member; finally, all that is required is to fit the rosette, which covers the wall recess, and the operating elements.
Since the depth of the wall recess and the depth at which the domestic pipes are laid in the wall vary, the way in which the connecting member is fastened in the wall recess must likewise be variable. In known concealed plumbing fixtures of the type mentioned at the beginning, the connecting member is adapted to the wall recess by fitting in wooden supports or similar mounts, the installation depth of the connecting member in the wall recess in particular being varied in this way. However, the adaptation with such wooden supports, which are only to be provided on site, is relatively time-consuming.
Adapting the fastening of the connecting element on wall linings, pre-wall systems or the like, to achieve an optimal installation depth, is not possible at all in this way.